Fresh water pump replacement: 3gpm or 4gpm?

[sailoppopotamus]

An ancient Shurflo 2095-232-244 on my boat is leaking so I'm looking for a replacement. I know I could probably just fix the leak, but the pump is 20-35 years old so I'd rather replace for peace of mind and keep the repaired one as a spare. The Shurflo Aqua King II comes in a 3gpm and a 4gpm version, while the current pump seems to be rated at 3.5gpm. Which should I get? The boat is 30ft, has two faucets, a calorifier, and a shower head on the transom. Most of the time only one faucet is in use, while occasionally we might use two at the same time.

 

[sailoppopotamus]

I also currently have a tiny accumulator which I plan to ditch entirely, as it occasionally leaks and seems woefully undersized to reduce pump cycling. The new Shurfo model claims to not need an accumulator.

 

[Plum]

An ancient Shurflo 2095-232-244 on my boat is leaking so I'm looking for a replacement. I know I could probably just fix the leak, but the pump is 20-35 years old so I'd rather replace for peace of mind and keep the repaired one as a spare. The Shurflo Aqua King II comes in a 3gpm and a 4gpm version, while the current pump seems to be rated at 3.5gpm. Which should I get? The boat is 30ft, has two faucets, a calorifier, and a shower head on the transom. Most of the time only one faucet is in use, while occasionally we might use two at the same time.

I think Sureflow quote US Gallons so their 3gpm is 2.5 imperial Gallons per min, which is 11 litres per minute. This is the flow rate of my Jabsco fresh water pump and for galley sink plus heads sink/shower and I find it perfectly acceptable.

 

[waynes world]

as @Plum says

 

[Macka1706]

An ancient Shurflo 2095-232-244 on my boat is leaking so I'm looking for a replacement. I know I could probably just fix the leak, but the pump is 20-35 years old so I'd rather replace for peace of mind and keep the repaired one as a spare. The Shurflo Aqua King II comes in a 3gpm and a 4gpm version, while the current pump seems to be rated at 3.5gpm. Which should I get? The boat is 30ft, has two faucets, a calorifier, and a shower head on the transom. Most of the time only one faucet is in use, while occasionally we might use two at the same time.

The "head" is more important than the flow if a larger. Higher boat. IE Height of lift the pump will push the water with stated flow rate.

 

[oldgit]

Do not be tempted to upgrade pump vastly to improve flow, stick to more or less same rating.
Some time ago replaced a failed pump in a rather ancient water system with one with considerably higher flow rate which happened to have lying around.
The increased pressure caused tap to water pipe unions to instantly fail, all of course in difficult to get at places..

 

[ChromeDome]

I fitted a deck-wash pump giving 26 LPM. All nice and well when using it for flushing, but it's pressure switch made it build up way to much stress on everything before reaching the switching point when closing the nozzle.

Fitted an external, adjustable, pressure switch. Inexpensive, btw.

 

[sailoppopotamus]

Thanks to everyone for the replies. I'm not looking to vastly upgrade as I realise it is likely to cause problems in the rest of the system. And besides, it's hard enough as it is to convince people to be frugal with their water consumption. I was actually leaning towards the smallest of the two but was having second thoughts that it might be a bit underpowered. But @Plum seems happy with his setup so my fear is probably unwarranted.

 

[V1701]

I've just replaced an old pump with a SEAFLO 41 Series 12V 3.3 gpm 35 psi, £75 from Chas Newens Marine, other outlets asking up to twice that for the same pump so do really shop around for the best price whatever pump you choose...